Differentially-connected exploring-coils.



J. B. TAYLOR.

DIFFERENTIALLY CONNECTED EXBLORING COtLS. APPLICATION FILED SEPT. 28,1915.

1,297,929. Patented Mar. 18,1919.

Poaitive- Shark Circuit.

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UNITED STATES PATENT OFFICE.

JOHN B. TAYLOR, OF SCHENECTADY, YORK, ASSIGNOR.TO GENERAL COMPANY, ACORPORATION OF NEW YORK.

DIFFmENTIALLY-CONNECTED EXPLORINGyCOTLS.

Specification of Letters Patent. Patented Mar. 18, 1919.

Application filed September- 28, 1915. Serial R0. 58,120.

To all whom it may concern:

citizen ofthe United States, residin at Schenectady, count ofSchenectady, tate of New York, have invented certain new and usefulImprovements in Differentially-Connected Exploring-Coils, of which thefollowing is a specification.

My invention relates to electric distribution systems and has for itsobject an im-' proved method and the provision of means for definitelylocating faults or grounds in One method employed for locating concealedgrounds or faults in conductors has been to supply the faulty conductorwith an alternating current suitable for inducing an indicating currentin an induction. coil connected to a telephone receiver or otherindieating means, which induction coil is adapted to be carried along inproximity to the grounded conductor, the presence of current in theconductor being indicated by the musical tone or hum of the telephonereceiver. When a fault or ground. was reached there might be adiminution of sound in the telephone which condition would continue foran indefinite distance beyond the .fault due to the fact that thecurrent after reaching the fault would still follow the cable because ofthe metal sheathing ordinarily used for such conductors. For thisreasonand for other electrical circuit conditions great diflicui hasbeen frequently experienced in definite y loeating the faulty point.

It is the object of'my invention to provide means for more definitelylocatin faults in conductors, and this I accomplish y means of twoexploring coils which are difierentially connected to a telephonereceiver or other sensitive current-responding device, the coils beingseparated by a substantial distance in the d1rection-of the length ofthe cable, preferably several feet and adapted to be carried on a motorcar or truck which may be driven or otherwise carried alon the route ofthe faul cable which is supp 'ed-with current suitab e for givingindication by induced current in the exploring 00115. For the testingcurrent for the affected cable, I prefert'o employ an alternatingcurrent of hi h frequency. such as is producedby a- 500 cyc e generator.By the arrangement of coils described, absence of sound corface of theexploring coils; and Fig. 3 shows theconnecresponding to the testingcurrent occurs in ELECTRIC case each coil is'equally exposed to the testmg current in the cable; '23. 6., so long as the v magnitude and phaseof the current is the due to the fact that the differential action ofthe current induced in the two coils does not become zero as is the casewhen the two I coils are equally exposed to'the current of .the samemagnitude and phase. This arrangement produces a very sensitiveindicatmg, means, as even a slight ground on the rents in the two coils.

The invention will be more clearly understood by referring to theaccompanying drawing, in which Figure 1 illustrates diagrammatically mymethod of locating faults; Fig. 2 shows a cross-section through an un-'conductor will cause unequal induced. curderground cable duct with anindication of. v

the magnetic field extending above the suround and cutting one of thetions of a preferred form of control switches.

Referring to Fig. 1 of the accompanying drawing, 1 indicatesanunderground conductor having a grounded point 2, which it is desired tolocate. For the purpose of de- 'tecting the fault 2, the conductor isconnected to one side of a generator 3, suitable for supplying it withinducing current, the

other side of the generator being connected to ground. The exploringcoils 4 and 5 are differentially connected to the telephone receiver 6.The coils are carried over the route of the conductor 1, preferably bymounting them'on-a motor tnu'ck orother vehicle and they are thusexposed to the magnetic field of the testing current as illustrated inFig. 2. The difi'erential action of the current in the two inductioncoils, as stated above, being such as to neutralize each other andproduce no sound at the receiver so long as they are equally exposed tothe magnetic field of the testing current, but as the coil 5 reaches andpasses the grounded point 2 in-the con-ductor the current induced 1n thecoil 5 decreases in magnitude .and a sound is produced at -.the receiver6, thus definitely indicating the location of the fault or ground Forcertain cornloinations of conductor electrostatic capacity and inr'oedances of several p arallel return ciruits the current be ond thegrounded fault 5 may he equa to or, in unusual cases, even than thecalole or n on the side of the fault. This condition Will not make thedevice inoperative unless the n side beyond currents are equal and ofthe same time ohase, con 'tion so unusual t at it i ll'lVBlllllOll 2 58ll Tl l cuttin in out one of the coils when no sound is i s w, T. 7 -L Ma 13 H Y) L sure e is close to the line Cl one o 1 1 i r 20 LLllfiLElthe.

test to mass sure that Q has not heen discontinued or broken :ooint. Asstatec sleeve the coils when d n rentiall r connected and equally I, 1'7 a or i i r UL ante eacn chaos and no sound is c at the tele nereceiver; the E t 1e coils an indication illustrated d omatically aswitching" I rangenient ;or varying the connections or the exploringcoils i and my M21, 1. n r E l J i113 switches T and o are creiera 7 ora ype u ed on telephone switch'hoards and 35 comprise short pivotedlevers indicated at 9 and 10 resoectively, which are easily l7 i wlelinger into any one .x. .L ated in the the rane short-circuit in Whi rthe oil 13 out on and negative in which the the con reversed. hrowrnalres the erect the GODS additire gives more definite indicatl w n o n'v or reefoie curre Is. A closcd ousnmodifications which do not departfrom spirit and scope of invention.

W l claim as new and desire to secure a substantial distance apart alongthe length of the cor l .ctor and adapted to he carried along proximityto the conductor and a s nsitive current responding device connectedseries with said coils, said coils so connected that the currentsinduced norma ly i the two coils tend to flow oppo directions throughsaid current responsiv device.

for locating a in a conductor ,Jil' oned with suitable inducing curr 1W0 induction coils spaced ubstantial cstance apart alon the length ofthe conductor a d adapted to he carried along pl'OXllflltj to the faultyconductor and sensitive current responding device l series with saidcoils, said coils :nected that the currents induced e two coils tend toFlow in ions through said current reinduction coils.

eating a fault in a conduca suitable inducing cu;- nt cozn r sing twoinduction coils spaced tic distance apart along the length e conductorand adapted he carried in pron city to the conductor, an.c sensitivecurrent responding dev ce being so connected that the currents inducednormally in the coils tend to flow in opposite directions through saidcurrent responsive device, and means for obtaining indication of theinducing current cornprising switching means for varying the connections0* the two induction coils.

insane for locating a fault in a conductor comprising a source ofcurrent or suping a suitable inducing cur out to the conector pair ofinduction coils adapted to carried along in proxrn ity to toe iaulty J-n a a conductor o current responding device ted in circuit with saidcoils said coils loc f g so connects to the current responding ElEVlCSand so spaced i-rom eacn ot er along the length or 1e cable that whenTooth coils zhe fault and the source of current suostantially In currentwill flour in the current "responding" device and when coils are onopposite sides he fault appreciable current will in the our respond ngdevice.

I; cans for locating a fault in a conducr comprising a source or currentfor supplying suitable inducing current to the conducton a pair ofinduction coils adapted to he *ied alo in proximity to the faultyconductor and a current responding device connected series with saidcoils, said coils being spaced a substantial distance along the lengthof the conductor, the axes c: said coils e itending transversely of theof he conductor Without intersec and coils heing so nd means forcircuit- -ected in series with said coils, said coils ice i that thecurrents induced normally in the two coils tend to flow in oppositedirections through said current responding device.

6. Means for locating a fault in an under-- rents induced normally inthe two coils tend to flow in opposite directions through said currentresponding device.

7. The method of locating a fault in a conductor which consists insupplying a suitable inducing current to said conductor and carry ingalong the length of the conductor at substantially equal distancestherefrom a pair of differentially connected induction coils which areseparated by a substantial distance until an indication is obtained in acurrent responding device connected to said coils.

8. The method of locating a fault in a conductor which consists insupplying a suitable inducing current to said conductor and carryingalong the length of the cable a pair of induction coils which areseparated from each other by a' substantial distance and so connected toa current responding device that when both coils are between the faultand the source of current substantially no current will flow in thecurrent responding device, and when the coils are on opposite sides ofthe fault an appreciable current will flow in the current respondingdevice.

9. The method of locating a fault in an underground conductor whichconsists in supplying a suitable inducing current to said conductor andcarrying along thesurface of the earth above said conductor in thedirection through which the conductor extends and at substantially equaldistances therefrom a pair of differentially connected induction coilsseparated by a substantial dis tance until an indication is obtained ina current responding device connected to said coils.

In witness whereof, I have hereunto set my hand this 27th day ofSeptember, 1915.

JOHN B. TAYLOR.

